We can use the top-down approach for this estimate:

Step 1: Estimate the total population of the United States.

The population of the United States is approximately 330 million.

Step 2: Estimate the percentage of the population that uses the internet.

In the U.S., about 90% of the population has access to the internet. That gives us approximately 297 million internet users (330 million * 90%).

Step 3: Estimate the number of these who listen to music online.

Online music streaming is very popular. Let's assume 70% of internet users listen to music online. That's approximately 208 million online music listeners (297 million * 70%).

Step 4: Estimate the percentage of these users who subscribe to Apple Music.

Apple Music is one of the most popular music streaming services, but there's a lot of competition with Spotify, Pandora, and others. Let's estimate that 25% of online music listeners use Apple Music. This gives us approximately 52 million Apple Music subscribers (208 million * 25%).

So, the estimated number of Apple Music subscribers in the United States is around 52 million.